Variable drive apparatus

ABSTRACT

Apparatus for imparting various rotational motions to a driven member in which a constantly rotating driving member transmits a predetermined angular velocity to the driven member by means of a frictional coupling. The angular velocity of the driven member is varied by overcoming the driving torque applied to the driven member by the frictional coupling. Means cooperating with the driving and driven members serve, respectively, to brake and to reverse the rotational motion of the driven member.

United States Patent 1191 C aspari 1 VARIABLE DRIVE APPARATUS [75]Inventor:

[73] Assignee: Burroughs Mich.

22 Filed: Nov. 27, 1970 21 App1.No.:93,339

Georg K. Caspari, Plymouth, Mich.

Corporation, Detroit,

52 U.S.Cl ..197/82,197/16,l97/84R, 197/90, 197/176 51 Int.Cl. ..B4lj19/00 [58]- Field of Search ..197/16, 19, 20, 82, 84, 84 A, 197/84 B,90, 89, 176, 177, 178, 179

[56] References Cited UNITED STATES PATENTS 3,313,389 4/1967 Cralle..197/16 X 3,578,129 5/1971 Katu ...197/187 X 3,315,776 4/1967 Barkdollet a1. 197/82 X 3,554,347 1/1971 Perkins ..197/87 UX 1 Feb. 6, 19733,313,387 4/1967 Lenney ..197/84 X 3,225,886 12/1965 Cetran et a1..197/84 2,704,591 3/1955 Bogert 197/90 X 2,886,160 5/1959 Frey ..197/84Primary Examiner--Robert E. Pulfrey Assistant ExaminerR. T. RaderAtt0rneyl(enneth L. Miller and Edwin W. Uren [57] ABSTRACT Apparatus forimparting various rotational motions to a driven member in which aconstantly rotating driving member transmits a predetermined angularvelocity to the driven member by means of a frictional coupling. Theangular velocity of the driven member is varied by overcoming thedriving torque applied to the driven member by the frictional coupling.Means cooperating with the driving and driven members serve,respectively, to brake and to reverse the rotational motion of thedriven member.

11 Claims, 4 Drawing Figures PATENTEDFEB s 1975 SHEET 2 OF 2 VARIABLEDRIVE APPARATUS BACKGROUND OF THE INVENTION This invention relatesgenerally to apparatus for imparting variable rotational motions to adriven member and, more particularly, to apparatus for controllablytranslating a print carrier along a print line in a printing machine.

In a single element type printing machine, such as an impacting -ballprinter, it is required that the print elementor ball be translatedalong a print line adjacent to a platen for printing characters in adesired format upon a medium interposed between the print element andthe platen. A common means for so displacing a print element is byengaging it with a rotatable screw so that the speed and direction ofrotation of the screw varies the speed and direction of lineartranslation of the print element. The control of the rotational motionof the screw is a task requiring a high degree of precision, for thespacing of printed characters, margins, and all other spacing variablesin a printing format are dependent upon precise translation of the printelement. In a situation where the printing element prints severalsuccessive characters on-the-fly the element must be moved at a speedsynchronized with the electronically established print rate andcharacter decoding process. In other types of printers where the printelement is escaped, accurate control of the stops and starts of theprint element must be maintained. In orderto move along the print linefor a relatively long distance without printing a character, the printelement must be moved as rapidly as feasible to cut the time thatprinting is held in abeyance. Also the print element must be capable ofback spacing, as well as returning from a tabulated position over a longdistance at a high rate of speed to a starting print position. Furthercomplicating the requirements of a lead screw rotating apparatus, areconsiderations of print element acceleration and deceleration which mustbe given attention to avoid undue strain on the printing apparatus aswell as for purposes of synchronizing the print element position with adesired printing operation.

SUMMARY OF THE INVENTION Accordingly, it is a primary aim of thisinvention to carry out'all of the aforementioned requirements of a printelement positioning apparatus in an inexpensive, reliable and efficientmanner.

More particularly, it is an object of the present invention toaccomplish all of the aforementioned functions in conjunction with onesingle-speed driving means.

It is a correlated object of the invention to utilize the same drivingmeans for the print element positioning apparatusas is used by theprinting machine for print decoding, such that carrier travel is alwayssynchronized with the decoding process.

It is further an object of the invention to effect a change in printelement translation velocity by the engagement of a single clutch.

It is still another object of the invention to achieve uniformacceleration of the printing element in escapement and rapid two-stageacceleration in tabulation and return.

A further object of the invention is to decelerate a tabulating orreturning print element in two stages in order to avoid excessive stresson the system, while at the same time facilitating high speed movementof the print element.

In accordance with the invention, an electronic printing machine isprovided with a print decoder and a timing unit which mechanicallypositions the print element of the machine. The mechanical energy forcarrying out this function is derived from a constant speed drivingmeans. A driving member of a variable drive apparatus is coupled to thedriving means for synchronous rotation therewith. For imparting variousrotational motions to a driven member that in turn moves a print elementcarrier, the driving member is coupled to the driven member by avariable coupling means. This means is responsive to electronic carriercontrol signals for imparting predetermined rotational motions to thedriven member. All movements of the driven member, and consequently ofthe print element carrier, are maintained in constant synchronizationwith the decoding process.

Another important aspect of the invention is the manner in which thevariable coupling means transforms the constant rotation of thedrivingmember into the many different motions required by the printingformat. In particular, two rotational speeds of the driven member areattained by coupling an input side of a clutch to the driving member,thus driving the input member at a predetermined second angularvelocity. The driven member is coupled to the driving member by means ofa friction coupling which imparts a predetermined first angular velocityto the driven member. The clutch is connected to the driven member suchthat engagement of the clutch overcomes the driving torque of thefriction coupling and changesthe rotational speed of the driven memberto the second predetermined angular velocity.

BRIEF DESCRIPTION OF THE DRAWINGS timing relationships of the severalcomponent parts of the variable drive apparatus.

DETAILED DESCRIPTION OF THE DRAWINGS Turning now to the drawings hereinlike reference characters designate identical elements in each of thefour figures, and particularly to FIG. 1, there is shown in schematicform the preferred carrier control apparatus incorporated in anelectronic printingmachine'. In such a printing machine a print elementcarrier 10 is translatable along a predetermined print line by means ofa lead screw 12 to which the carrier is engaged by any suitable means.The characters that are to be printed and the order of their printing isstored in an associated memory of a central processor 14 which transmitssuch information in electronically coded form to a print decoder andtiming unit 16. In order to correctly position the print element 18 ofthe carrier and to actuate a printing impact of the element, the printdecoder and timing unit 16 decodes the electronic informationtransmitted to it by the central processor 14 and communicates thedecoded information via a mechanical linkage to the carrier. The powerfor driving the mechanical linkage of the carrier 10 is provided by aconstant speed motor 20 coupled to the print decoder and timing unit 16by a driving member or shaft 22.

The translation of the carrier 10 along the print line is controlled bythe rotation of the lead screw 12 that is in turn driven by variabledrive apparatus 24 coupling the driving member 22 with the screw 12. Inorder to effect the required variation in angular velocity of the leadscrew 12, the variable drive apparatus 24 in response to electronicsignals from the carrier drive control logic 30, translates theunidirectional constant velocity of the driving member or shaft 22 to abidirectional, multi-velocity output. The variable drive apparatus 24also serves to brake the rotation of the lead screw 12 for varyingperiods of time to achieve an escapement or backspace motion of thecarrier 10.

The carrier drive control logic maintains a record of the position ofthe carrier 10 with the assistance of a position readout device 32coupled to the lead screw 12. The next desired carrier position iscommunicated to the carrier drive control logic 30 from the centralprocessor 14 and compared with the present carrier position. When thecarrier 10 is located a predetermined distance from the desiredposition, the control logic 30 is programmed to generate certainelectrical control signals to the variable drive apparatus 24 tocorrectly position the carrier by rotating the lead screw 12. Carrierdrive control logic of the variety required is disclosed in a U.S. Pat.No. 3,403,386 entitled Format Control issued to Perkins et al and havingcommon ownership herewith.

In FIG. 2 is illustrated the preferred embodiment of the variable driveapparatus 24. As was described in connection with FIG. 1, a drivingmember or shaft 22 is rotatable by a motor at a substantially constantangular velocity about a longitudinal axis through the center of theshaft. The rotating driving shaft 22, as stated, is also coupled to theprint decoder and timing unit 16 (FIG. 1), so that the rotational motionimparted to the lead screw 12 is always synchronized with the decodingand timing operation of the printing machine. It is from thissynchronized driving shaft 22 that all carrier motion is ultimatelyderived. Variable coupling means, as hereinafter described, serves tovary the driving effect of the driving shaft 22 upon the lead screw 12.

For driving a driven member or shaft 26 at a first or slow angularvelocity, an annular geared rim 34 of a friction coupling 36 is engagedby means of a pinion 38 and idler gear 40 to the driving shaft 22. Thepinion gear 38 is firmly attached to rotate with the driving shaft 22and the idler gear 40 is independently supported to rotate in engagementwith both the pinion gear and the geared rim 34 of the friction coupling36. Rotation of the driving member 22 thus rotates the geared rim 34 ofthe friction coupling 36 in a common direction therewith and at apredetermined velocity.

An inner disk 42 of the friction coupling 36 has an outer peripherypositioned in slidable abutment with an inner periphery of the annulargeared rim 34 so that rotation of the geared rim frictionally engagesthe inner disk, thereby tending to rotate the disk with a torquedetermined by the frictional force between the abutting peripheries ofthe inner disk and the geared rim. Accordingly, the inner disk 42 mayrotate independently of the geared rim 34 if enough torque is applied tothe disk to overcome the frictional force between it and the geared rim.To permit the driven shaft 26 to rotate in one direction substantiallyindependently of the friction coupling 36, the inner disk 42 is coupledto the driven shaft by a one-way slip coupling, such as the overrunningspring clutch 44 illustrated in FIG. 3 (but blocked from view in FIG.2). The spring clutch 44 is configured in the form ofa spiral springhaving one end portion 46 wrapped about a sleeve 48 extending from theinner disk 42 of the friction coupling 36, and the other end portion 50wrapped about an enlarged section 52 of the driven shaft 26. The sleeve48 of the disk 42 is loosely mounted on the driven shaft 26 to rotateindependently thereof. Upon counterclockwise rotation of the frictioncoupling 36, as shown in FIG. 3, the sleeve 48 of the inner disk 42 isengaged by the spring clutch 44 to carry with it the driven shaft 26 inan effectively rigid fashion whereas a counterclockwise torque on thedriven shaft 26 tending to rotate it ahead of the friction couplingtends to disengage the spring clutch from the sleeve of the inner disk.The action of the spring clutch 44 operates to permit the angularvelocity of the driven shaft 26 to be increased without having toovercome the relatively high torsional resistance of the frictioncoupling 36.

The driven member 26 is rotated at an increased angular velocity by anelectromagnetic clutch 54 having an input member 56 coupled by a beltand pulley arrangement 58 to the driving shaft 22. The size of therespective pulleys determines the rate of angular velocity for the inputmember 56 of the electromagnetic clutch 54, that rate being greater thanthat of the friction coupling 36. Thus, when the electromagnetic clutch54 engages in response to an electrical signal from the carrier drivecontrol logic 30 (FIG. 1), an output member (not shown) of the clutch 54connected to the driven shaft 26 transmits the increased or secondpredetermined angular velocity to the driven member 26 by overcoming thedriving influence of the frictional coupling 36, as heretoforedescribed.

The driven member 26 is further connected to a rotation reversal meansthat is comprised of two similar electromagnetic clutches respectivelytermed the reverse clutch 60 and the forward clutch 62. An input member(not shown) of the forward clutch is attached to the driven shaft 26 torotate in the same direction therewith. A geared rim 64 of the inputmember of the forward clutch 62 engages a similar geared rim 66 of aninput member of the reverse clutch 60 for imparting an opposite rotationthereto. Both of these clutches 60-62 are coupled by means of a commonbelt 68 to a pulley 70 on the lead screw 12 so that the lead screw maybe rotated in a forward or reverse direction depending upon which of thetwo clutches are engaged.

The portion of the apparatus thus far described serves to control therotational motion of the driven member in two ways: rate and direction.There is another function however, that remains to be implemented inorder to precisely control the translation of the carrier along theprint line. That is, the carrier 10 must be stopped and started inprecise locations and at precise times. The preferred braking means isdescribed in detail i Burroughs Series L Field Engineering TechnicalManual, section 2, pages l18-l 19 in connection with Burroughs Models12000, L3000 and L4000 accounting computers. Briefly, the braking meansoperates to stop the rotation of the lead screw 12 by engaging a tooth72 ofa detent wheel 74 with bidirectional latches 7676, the detent wheelbeing attached to the lead screw for rotation therewith. Thebidirectional latches 7676 are biased into engagement with individualteeth 72 of the the detent wheel 74. There are two ways in which thelatches 7676 may be disengaged from the wheel 74, one resulting inintermittent disengagement and the other in continuous disengagement.The former is accomplished by actuating an interposing solenoid 78 whicheffectively engages the braking system with an eccentric cam 80 on thedriving shaft 22. The resulting camming action cyclically operatesthrough a mechanical linkage 82 to pull the latches 76--76 away from thedetent wheel at constant predetermined intervals. Continuousdisengagement is accomplished by actuating a pair of hold solenoids84-84 which magnetically pivot the latches 7676 away from the detentwheel 74 whenever the solenoidsare actuated. The actuation of the holdsolenoid 84 84 allows the lead screw 12 long periods of rotation fortabulation and return operations while the interposer solenoid 78 isactuated to initiate escapement or backspacing movement. A morecomprehensive explanation of the operation of the braking means inrelation to carrier movement will hereinafter be undertaken.

OPERATION In connection with the timing diagrams of FIG. 4, a preferredtiming relationship of the various elements of the variable driveapparatus 26 may be illustrated. A chain of timing pulses is generatedby the print decoder and timing unit 16 in synchronization with thedriving shaft 22 (FIG. 1). These pulses are used as a timing basis bythe carrier drive control logic in determining and generating the othersignals for initiating the various functions of the variable driveapparatus 24.

To initiate an escapement operation, a forward clutch engagement signalis generated by the carrier drive control logic 30 at the leading edgeof a timing pulse 86. Coincident with the initiation of the forwardclutch engagement signal the interposer solenoid 78 is activated byanothersignal from the carrier control logic 30. After the forwardclutch 62 is engaged, there is a slight hesitation before the eccentriccam 80 pulls bidirectional latches 76-76 out of engagement with thedetent wheel 74 in the manner heretofore described. During this slighthesitation the friction coupling 36 begins to slip, thereby applying apredetermined torsional load to the lead screw 12 so that disengagementof the latches 7676 effects a substantially uniform acceleration 88until it reaches the first angular velocity 90 determined by thenon-slip angular velocity of the driven member 26. As the eccentric cam80 rotates with the driving member 22, the bidirectional latches 76-76periodically engage each succeeding tooth 72 of the detent wheel 74 fora short period 92 in which a print command from the print decoder andtiming unit 16 activates an impact of the print element 18 of thecarrier 10 to print a character. Escapement continues cyclically withthe forward clutch 62 remaining engaged until after the last escapementcycle. Each time the bidirectional latches 7676 engage the detent wheel74, the inner disk 42 of the friction coupling 36 is. halted and theouter rim 34 remains driven, consequently prestressing theleadscrew 12with a predetermined torsional load that is used to accelerate the leadscrew to a predetermined angular velocity when the bidirectional latchesare cammed out of engagement with the detent wheel. A back space isaccomplished in the same manner as an escapement, the only differencebeing that instead of engaging the forward clutch 62, the reverse clutchis engaged to rotate the lead screw 12 in the opposite direction.

For tabulation of the print carrier 10 it is desirable that the carrierbe moved at an accelerated velocity in order to minimize lapses in theprinting operation. A tabulation process is begun in the same manner asan escapement, with the interposer solenoid 78 and the forward clutch 62activated simultaneously as at 94 in FIG. 4. After the interposersolenoid 78 has removed the bidirectional latches 7676 from engagementwith the detent wheel 74, the hold solenoids 84-84 are activated to holdthe bidirectional latches out of engagement with the detent wheel. Thehold solenoids 84-84 are not used to initially disengage thebidirectional latches 7676 in the preferred configuration, because theforce of the camming action initiated by the activation of theinterposer solenoid 78 is more precise in time and of greater magnitudethan the force that is applied by the hold solenoids 84-84. Such cammingaction provides a faster and more positive start of lead screw rotationand carrier motion. As the carrier 10 starts to accelerate, as at 96,under the influence of the friction coupling 36, the high speed clutch54 is engaged to increase the angular velocity of the driven member 26to the predetermined second velocity thereof as heretofore described.The carrier velocity 98 is thus determined by the angular velocityimparted to the driven shaft 26 by the high speed clutch 54. The carriercontinues to tabulate until some predetermined distance before a desiredstopping point is reached. At such time the high speed clutch 54 isdisengaged, as at 100 in FIG. 4. inherent drag in the system, includingthe resistance of the residual torque of the slipping spring clutch 44against the rotating driven shaft 26, serves to decelerate the leadscrew 12 to the first or slow angular velocity imparted to the screw bythe friction coupling 36. At a second predetermined distance of carriertravel after deceleration, the hold solenoid 84 is deactuated, as at102, and the bidirectional latches 7676 thereafter reengage the detentwheel 74 to brake the rotation of thelead screw 12, the rim 34 of thefriction coupling thereafter continuing to rotate independently of thedisk 42.

With a slight modification, the variable drive apparatus could beadapted for on-the-fly printing, in which the carrier would becontinuously moved during a printing operation rather than escaping asdescribed above. Such carrier movement may be effected in a similarmanner as tabulation, except the high speed clutch 54 would not beengaged. Rather, the rotational speed of the geared rim 34 of thefriction coupling 36 would be adjusted by the relative sizes of thepinion 38 and idler 40, to achieve a proper rate of angular velocity foron-the-fly carrier translation. In such an application the angularvelocity of the lead screw 12 would always be synchronized with thetiming of the print decoder and timing unit 16, consequently thecritical problem of synchronizing print rate and print elementpositioning with carrier translation is greatly simplified.

While the invention has been described in conjunction with a specificembodiment it is evident that many modifications and alternatives nottruely departing from the inventive concept residing therein will beapparent to those skilled in the art in light of the foregoingdescription. Accordingly, it is intended to embrace within the scope ofthe appended claims all such modifications and alternatives that residewith the inventive concept herein disclosed.

What is claimed is:

1. In a printing machine having a print decoder and timing unit fordecoding electrical signals representing a character to be printed by aprinting element, said unit being mechanically driven by a constantspeed driving means and effective to generate an electrical timing pulsein synchronization with said driving means, and having also carrierdrive control logic responsive to said timing pulse for generatingelectronic carrier control signals and variable drive apparatus fortranslating a carrier of said printing element along a print line, saidapparatus comprising,

a rotatable driving member coupled with said driving means forsynchronous rotation therewith, a rotatable driven member drivablyassociated with said driving member, a rotatable carrier driver coupledto said driven member, and variable coupling means drivably couplingsaid driving member with said driven member,

said variable coupling means said having at least two separate drivingconnections between said driving member and said driven member forrotatively driving the driven member in the same direction but atdifferent angular velocities thereby to translate said printing elementcarrier in one direction along the print line but at different speedsfor letter spacing and tabulation,

a rotation reversal connection between said driving member and saiddriven member for reversing the rotation of said carrier driver therebyto translate said printing element carrier in the opposite directionalong the print line,

brake means for stopping the rotation of said carrier driver thereby tohalt translational movement of said print element carrier, and

means for rendering each of said driving and reversal connections andsaid brake means responsive to individual ones of said electroniccarrier control signals, whereby the stopping, starting, speed anddirection of motion of the printing element carrier along the print lineis controlled in synchronization with said print decoder and timing unitin accordance with a predetermined printing format.

2. In a printing machine having a print decoder and timing unit fordecoding electrical signals representing a character to be printed by aprinting element, said decoder being mechanically driven by a constantspeed driving means and effective to generate an electrical timing pulsein synchronization with said driving means, and having also carrierdrive control logic responsive to said timing pulse for generatingelectronic carrier control signals, variable drive apparatus fortranslating a carrier of said printing element along a print line, saidapparatus comprising,

a driving member coupled with said driving means for synchronousrotation therewith, a driven member drivably associated with saiddriving member, a carrier driver coupled to said driven member, andvariable coupling means drivably coupling said driving member with saiddriven member, said variable coupling means being operative to vary thedriving effect of said driving member upon said driven member and saidcarrier driver in response to said electronic carrier control signals,said carrier thus being translated at a variable velocity along theprint line in synchronization with said print decoder and timing unit inaccordance with a predetermined printing format,

said variable coupling means comprising,

a friction coupling frictionally engaged with said driven member fortransmitting a first predetermined torque thereto,

a first means drivably coupling said driving member with said frictioncoupling for driving said driven member in a first direction at a firstpredetermined angular velocity,

an engageable clutch having an output member fixedly attached to saiddriven member for rotation therewith and an input member controllablyengageable into driving relationship with said output member in responseto a first electrical signal for transmitting a second predetermineddriving torque to said driven member,

second coupling means drivably coupling said input member of eachengageable clutch with said driving member for rotation of said inputmember in said first direction at a second predetermined angularvelocity, said second predetermined angular velocity being greater thansaid first predetermined angular velocity,

rotation reversal means coupled to said driven member and responsive toa second electrical signal for reversing the direction of rotation ofsaid carrier driver, and

braking means coupled to said carrier driver and responsive to saiddriving means and to a third electrical signal for braking therotational motion of said carrier driver and said driven member, wherebythe stopping, starting, speed and direction of angular motion of saidcarrier driver is controllable by corresponding ones of said electricalsignals.

3. in printing apparatus having means for varying the angular velocityof a driven member, said means comprising,

a driving member,

means for rotating said driving member at a constant angular velocity,

a friction coupling frictionally engaged with said driven member fortransmitting a first predetermined driving torque thereto,

first means drivably coupling said driving member with said frictioncoupling for driving said driven member at a first predetermined angularvelocity,

an engageable electromagnetic clutch having an output member fixedlyattached to said driven member for rotation therewith and further havingan input member controllably engageable into driving relationship withsaid output member for transmitting a second predetermined drivingtorque to the driven member, and

second means drivably coupling the said input member with said drivingmember for rotating said input member at a second predetermined angularvelocity in the same direction as applied by said first coupling meansbut at a greater velocity than said first predetermined angularvelocity, whereby the engagement of said engageable clutch overcomes thefirst predetermined driving torque of said friction clutch to rotatesaid driven member at said second predetermined angular velocity.

4. Apparatus as defined by claim 3 wherein said friction coupling iscomprised of an annular disk having a geared annular rim engaged withsaid first coupling means, said rim having an inner peripheryfrictionally engaged with the periphery of an inner disk, said innerdisk being drivably coupled to said driven member.

5. Apparatus as defined by claim 4 further including a one-way slipclutch for coupling the inner disk of said friction coupling with saiddriven member, said oneway slip clutch being rigidly engaged with saiddriving member for transmitting said first driving torque thereto, buteffective to disengage said friction coupling from said driving memberunder the influence of said second driving torque transmitted to saiddriven member by said engageable clutch.

6. A mechanism as defined by claim 5 wherein said one-way slip couplingis a spring clutch having one end portion coupled to said frictioncoupling and another end portion coupled to said driving member.

7. in printing apparatus, print carrier positioning mechanism includingmeans for varying the angular motion of a print carrier driver inresponse to corresponding electrical signals, said means comprising,

a driven member operatively coupled to said print carrier driver,

a driving member,

means for rotating said driving member at a constant angular velocity,

a friction coupling frictionally engaged with said driven member fortransmitting a first predetermined torque thereto,

a first means drivably coupling said driving member with said frictioncoupling for driving said driven member in a first direction at a firstpredetermined angular velocity,

an engageable clutch having an output member fixedly attached to saiddriven member for rotation therewith and an input member controllablyengageable into driving relationship with said output member in responseto a first electrical signal for transmitting a second predetermineddriving torque to said driven member,

second coupling means drivably coupling said input member with saiddriving member for rotation of said input member in said first directionat a second predetermined angular velocity, said second predeterminedangular velocity being greater than said first predetermined angularvelocity,

rotation reversal means coupled to said driven member and responsive toa second electrical signal for reversing the direction of rotation ofsaid print carrier driver, and

braking means coupled to said print carrier driver and responsive tosaid driving means and to a third electrical signal for braking therotational motion of said carrier driver and said driven member wherebythe stopping, starting, speed and direction of angular motion of saidprint carrier driver is controllable by corresponding ones of saidsignals.

8. Apparatus as defined in claim 7 further comprising a one-way slipclutch for drivably engaging said friction coupling with said drivenmember at said first predetermined angular velocity, said one-way slipclutch being operative to disengage from said friction coupling whensaid driven member is accelerated by said engageable clutch, saidone-way slip clutch remaining disengaged until said driven memberdecelerat'es to an angular velocity equal to said first predeterminedangular velocity.

9. Apparatus as defined in claim 8 wherein said oneway slip clutch is aspring clutch having one end portion coupled to said friction couplingand another end portion coupled to said driven member.

10. In printing apparatus, print carrier positioning mechanism includingmeans for varying the angular motion and direction of a print carrierdriver in response to corresponding electrical signals, said meanscomprising,

a driven member operatively coupled to said print carrier driver,

a driving member normally rotatable at a constant velocity,

a first coupling means drivingly coupling said driving member with saiddriven member for driving the latter in a first direction at a firstangular velocity,

a second coupling means for disengagingly coupling said driving memberwith said driven member and operable when coupled thereto to drive thelatter in the same direction as said first coupling means but at adifferent angular velocity, said second coupling means being responsiveto a first electrical signal for performing its aforesaid couplingfunction,

rotation reversal means disengagingly coupling said driven member withsaid print carrier driver'and responsive to a second electrical signalfor reversing the direction of rotation of said print carrier driver,and i braking means coupled to said print carrier driver and responsiveto said driving means and to a third electrical signal for braking therotational motion of said carrier driver and said driven member wherebythe stopping, starting, speed and direction of angular motion of saidprint carrier driver is controllable by corresponding ones of saidsignals.

33 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3,75, 4 Bas d Feb. 6, 1973 Invenfm-(s) Georg Karl Caspari It is certifiedthat error appears in the above-ideantiffned patent and that saidLetters Patent are hereby corrected as shown below:

Col. 7, line 32, after "and" insert --the printing machineline 3 after"and" insert --further having- Col. 8,line I, delete "decoder" andsubstitute therefore --unj line 7, after "and" insert --the machine-;line 9, after the comma insert --and having-.

Signed and sealed this 3rd day of July i973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Rene Tegtmeyer I I I Attesting Officer ActinCommissioner -of Patents

1. In a printing machine having a print decoder and timing unit fordecoding electrical signals representing a character to be printed by aprinting element, said unit being mechanically driven by a constantspeed driving means and effective to generate an electrical timing pulsein synchronization with said driving means, and having also carrierdrive control logic responsive to said timing pulse for generatingelectronic carrier control signals and variable drive apparatus fortranslating a carrier of said printing element along a print line, saidapparatus comprising, a rotatable driving member coupled with saiddriving means for synchronous rotation therewith, a rotatable drivenmember drivably associated with said driving member, a rotatable carrierdriver coupled to said driven member, and variable coupling meansdrivably coupling said driving member with said driven member, saidvariable coupling means said having at least two separate drivingconnections between said driving member and said driven member forrotatively driving the driven member in the same direction but atdifferent angular velocities thereby to translate said printing elementcarrier in one direction along the print line but at different speedsfor letter spacing and tabulation, a rotation reversal connectionbetween said driving member and said driven member for reversing therotation of said carrier driver thereby to translate said printingelement carrieR in the opposite direction along the print line, brakemeans for stopping the rotation of said carrier driver thereby to halttranslational movement of said print element carrier, and means forrendering each of said driving and reversal connections and said brakemeans responsive to individual ones of said electronic carrier controlsignals, whereby the stopping, starting, speed and direction of motionof the printing element carrier along the print line is controlled insynchronization with said print decoder and timing unit in accordancewith a predetermined printing format.
 1. In a printing machine having aprint decoder and timing unit for decoding electrical signalsrepresenting a character to be printed by a printing element, said unitbeing mechanically driven by a constant speed driving means andeffective to generate an electrical timing pulse in synchronization withsaid driving means, and having also carrier drive control logicresponsive to said timing pulse for generating electronic carriercontrol signals and variable drive apparatus for translating a carrierof said printing element along a print line, said apparatus comprising,a rotatable driving member coupled with said driving means forsynchronous rotation therewith, a rotatable driven member drivablyassociated with said driving member, a rotatable carrier driver coupledto said driven member, and variable coupling means drivably couplingsaid driving member with said driven member, said variable couplingmeans said having at least two separate driving connections between saiddriving member and said driven member for rotatively driving the drivenmember in the same direction but at different angular velocities therebyto translate said printing element carrier in one direction along theprint line but at different speeds for letter spacing and tabulation, arotation reversal connection between said driving member and said drivenmember for reversing the rotation of said carrier driver thereby totranslate said printing element carrieR in the opposite direction alongthe print line, brake means for stopping the rotation of said carrierdriver thereby to halt translational movement of said print elementcarrier, and means for rendering each of said driving and reversalconnections and said brake means responsive to individual ones of saidelectronic carrier control signals, whereby the stopping, starting,speed and direction of motion of the printing element carrier along theprint line is controlled in synchronization with said print decoder andtiming unit in accordance with a predetermined printing format.
 2. In aprinting machine having a print decoder and timing unit for decodingelectrical signals representing a character to be printed by a printingelement, said decoder being mechanically driven by a constant speeddriving means and effective to generate an electrical timing pulse insynchronization with said driving means, and having also carrier drivecontrol logic responsive to said timing pulse for generating electroniccarrier control signals, variable drive apparatus for translating acarrier of said printing element along a print line, said apparatuscomprising, a driving member coupled with said driving means forsynchronous rotation therewith, a driven member drivably associated withsaid driving member, a carrier driver coupled to said driven member, andvariable coupling means drivably coupling said driving member with saiddriven member, said variable coupling means being operative to vary thedriving effect of said driving member upon said driven member and saidcarrier driver in response to said electronic carrier control signals,said carrier thus being translated at a variable velocity along theprint line in synchronization with said print decoder and timing unit inaccordance with a predetermined printing format, said variable couplingmeans comprising, a friction coupling frictionally engaged with saiddriven member for transmitting a first predetermined torque thereto, afirst means drivably coupling said driving member with said frictioncoupling for driving said driven member in a first direction at a firstpredetermined angular velocity, an engageable clutch having an outputmember fixedly attached to said driven member for rotation therewith andan input member controllably engageable into driving relationship withsaid output member in response to a first electrical signal fortransmitting a second predetermined driving torque to said drivenmember, second coupling means drivably coupling said input member ofeach engageable clutch with said driving member for rotation of saidinput member in said first direction at a second predetermined angularvelocity, said second predetermined angular velocity being greater thansaid first predetermined angular velocity, rotation reversal meanscoupled to said driven member and responsive to a second electricalsignal for reversing the direction of rotation of said carrier driver,and braking means coupled to said carrier driver and responsive to saiddriving means and to a third electrical signal for braking therotational motion of said carrier driver and said driven member, wherebythe stopping, starting, speed and direction of angular motion of saidcarrier driver is controllable by corresponding ones of said electricalsignals.
 3. In printing apparatus having means for varying the angularvelocity of a driven member, said means comprising, a driving member,means for rotating said driving member at a constant angular velocity, afriction coupling frictionally engaged with said driven member fortransmitting a first predetermined driving torque thereto, first meansdrivably coupling said driving member with said friction coupling fordriving said driven member at a first predetermined angular velocity, anengageable electromagnetic clutch having an output member fixedlyattached to said driven member for rotation therewith and further havingan input mEmber controllably engageable into driving relationship withsaid output member for transmitting a second predetermined drivingtorque to the driven member, and second means drivably coupling the saidinput member with said driving member for rotating said input member ata second predetermined angular velocity in the same direction as appliedby said first coupling means but at a greater velocity than said firstpredetermined angular velocity, whereby the engagement of saidengageable clutch overcomes the first predetermined driving torque ofsaid friction clutch to rotate said driven member at said secondpredetermined angular velocity.
 4. Apparatus as defined by claim 3wherein said friction coupling is comprised of an annular disk having ageared annular rim engaged with said first coupling means, said rimhaving an inner periphery frictionally engaged with the periphery of aninner disk, said inner disk being drivably coupled to said drivenmember.
 5. Apparatus as defined by claim 4 further including a one-wayslip clutch for coupling the inner disk of said friction coupling withsaid driven member, said one-way slip clutch being rigidly engaged withsaid driving member for transmitting said first driving torque thereto,but effective to disengage said friction coupling from said drivingmember under the influence of said second driving torque transmitted tosaid driven member by said engageable clutch.
 6. A mechanism as definedby claim 5 wherein said one-way slip coupling is a spring clutch havingone end portion coupled to said friction coupling and another endportion coupled to said driving member.
 7. In printing apparatus, printcarrier positioning mechanism including means for varying the angularmotion of a print carrier driver in response to corresponding electricalsignals, said means comprising, a driven member operatively coupled tosaid print carrier driver, a driving member, means for rotating saiddriving member at a constant angular velocity, a friction couplingfrictionally engaged with said driven member for transmitting a firstpredetermined torque thereto, a first means drivably coupling saiddriving member with said friction coupling for driving said drivenmember in a first direction at a first predetermined angular velocity,an engageable clutch having an output member fixedly attached to saiddriven member for rotation therewith and an input member controllablyengageable into driving relationship with said output member in responseto a first electrical signal for transmitting a second predetermineddriving torque to said driven member, second coupling means drivablycoupling said input member with said driving member for rotation of saidinput member in said first direction at a second predetermined angularvelocity, said second predetermined angular velocity being greater thansaid first predetermined angular velocity, rotation reversal meanscoupled to said driven member and responsive to a second electricalsignal for reversing the direction of rotation of said print carrierdriver, and braking means coupled to said print carrier driver andresponsive to said driving means and to a third electrical signal forbraking the rotational motion of said carrier driver and said drivenmember whereby the stopping, starting, speed and direction of angularmotion of said print carrier driver is controllable by correspondingones of said signals.
 8. Apparatus as defined in claim 7 furthercomprising a one-way slip clutch for drivably engaging said frictioncoupling with said driven member at said first predetermined angularvelocity, said one-way slip clutch being operative to disengage fromsaid friction coupling when said driven member is accelerated by saidengageable clutch, said one-way slip clutch remaining disengaged untilsaid driven member decelerates to an angular velocity equal to saidfirst predetermined angular velocity.
 9. Apparatus as defined in claim 8wherein saiD one-way slip clutch is a spring clutch having one endportion coupled to said friction coupling and another end portioncoupled to said driven member.
 10. In printing apparatus, print carrierpositioning mechanism including means for varying the angular motion anddirection of a print carrier driver in response to correspondingelectrical signals, said means comprising, a driven member operativelycoupled to said print carrier driver, a driving member normallyrotatable at a constant velocity, a first coupling means drivinglycoupling said driving member with said driven member for driving thelatter in a first direction at a first angular velocity, a secondcoupling means for disengagingly coupling said driving member with saiddriven member and operable when coupled thereto to drive the latter inthe same direction as said first coupling means but at a differentangular velocity, said second coupling means being responsive to a firstelectrical signal for performing its aforesaid coupling function,rotation reversal means disengagingly coupling said driven member withsaid print carrier driver and responsive to a second electrical signalfor reversing the direction of rotation of said print carrier driver,and braking means coupled to said print carrier driver and responsive tosaid driving means and to a third electrical signal for braking therotational motion of said carrier driver and said driven member wherebythe stopping, starting, speed and direction of angular motion of saidprint carrier driver is controllable by corresponding ones of saidsignals.